A gas turbine includes a compressor, a combustor, and a turbine. Air collected from an air inlet is compressed in the compressor to be turned into high temperature and high pressure compressed air. Fuel is supplied to the compressed air for combustion in the combustor. The high temperature and high pressure combustion gas drives the turbine, further to drive a generator that is connected to the turbine. The turbine includes a plurality of nozzles and rotor blades arranged in an alternating manner within a casing, and the rotor blades are driven by the combustion gas to drive an output shaft that is connected to the generator in rotation. The combustion gas that has driven the turbine is converted to a static pressure by way of a diffuser included in an exhaust casing, and then released into the air.
Recently, a gas turbine has come to be demanded to be highly efficient and have a high output, and there is a tendency that the temperature of the combustion gas guided to the nozzles and the rotor blades is increased more than ever. Therefore, generally, a cooling passage is formed inside the nozzles and the rotor blades, and a cooling medium, such as air or steam, is allowed to flow in the cooling passage to cool the nozzles and the rotor blades, to ensure the heat resistance as well as to enable an increase in the temperature of the combustion gas so that the output and the efficiency are improved.
For example, in the rotor blades, a plurality of rotor blade bodies each having a cooling passage formed inside is arranged along and fixed to an outer circumference of the turbine disk in a circumferential direction. Cooling holes are formed on the turbine disk in a radial direction, and leading ends of the cooling holes are connected to the cooling passages in the rotor blade bodies. The cooling medium is supplied into the cooling holes from the base ends thereof, and flows inside the cooling passage via the cooling holes to cool the rotor blade bodies.
Such a turbine cooling structure is disclosed in Patent Document 1 below, for example.
[Patent Document 1] Japanese Patent Application Laid-open No. H8-218804